Medical snares are typically employed to extract foreign and/or undesired material from vessels within the body. For example, medical snares may be used for extracting blood clots from within the cardiovascular system, as well as stones from within the urinary and biliary systems. Similarly, medical snares may be used for removing foreign objects from the body. For example, medical snares may be used to remove objects such as stents, filters and catheters that have been inadvertently placed, which have broken free, and/or that may have migrated from other locations from within the body.
In a typical procedure utilizing a medical snare, a vascular sheath is inserted into the patient, for example into the femoral artery, to provide access to the cardiovascular system of the patent. A catheter is inserted through the vascular sheath, and a guide wire is inserted through the catheter. The guide wire is advanced through the vascular system to the desired location, e.g., to the vicinity of the clot to be removed. Once the guide wire has been positioned in the desired location, the catheter is advanced over the guide wire, thereby delivering the catheter to the area of interest, such as the vicinity of the clot, in the foregoing example. Once the guide wire has been removed from the catheter, a snare may be introduced through the catheter to the desired location. The snare, which may include one or more loops is advanced at least partially out of the catheter to capture the clot. Once the clot has been captured by the snare, the snare and catheter may be retracted as a unit, and ultimately removed from the patient via the vascular sheath.
Unfortunately, it is not uncommon that, once the catheter has been delivered to the site of interest, the catheter may move from the ideal position during the removal of the guide wire and subsequent advancement of the snare through the catheter. Such movement typically results in a failed snaring attempt. When the snaring attempt is unsuccessful, the snare must be removed from the catheter. The guide wire must then be reinserted through the catheter, and the catheter must be repositioned. Once the catheter has been repositioned, the snare may again be inserted through the catheter, and another snaring attempt may be made. Attempts to reposition the catheter without first removing the snare and reinserting and repositioning the guide wire may often damage the vessel, either by the leading edge of the catheter or by the snare itself if the snare is used out in front of the catheter during the repositioning attempt.
The need to “start over,” by removing the snare, reinserting the guide wire, repositioning the catheter, and then reinserting the snare, in order to make another snaring attempt following a failed capture is undesirable. Such repeated snaring attempts are frustrating to the medical professionals carrying out the procedure, are time consuming, and potentially harmful to the patient, necessitating unnecessary radiation exposure. This is especially true considering the seriousness of the circumstances that necessitate the snaring procedure in the first place, e.g., a blood clot restricting blood flow to critical anatomy or presenting a risk of dislodging and moving to a critical region.